This invention relates to a process for the production of micro-organisms. Many micro-organisms are known which can utilise hydrocarbons or certain oxygenated or other derivatives thereof as their carbon and/or energy source. The dried biomass obtainable by the cultivation of such micro-organisms, often referred to as single cell protein, is rich in protein and can be used as a possible foodstuff or food supplement for man and animals. Of particular interest in this connection are micro-organisms which are capable of utilising gaseous organic compounds containing one or more carbon atoms in their molecules, for example methane.